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THIMBY life: cozy, fun, labor-intensive, progressive, living lab. The past 4 months have been exciting for the tiny house transition from construction to living site. Yes, there were nights when we came home to find our water supply run over by a car and leaking all over the parking lot, or when we couldn’t get the heat pump to run (someone knocked the Arduino control system off the wall...), or couldn’t figure out why the inverter-battery system wasn’t working. Usually it was a quick fix, under an hour, but the energy system was a bit more complicated. The battery wasn’t charging, so the company sent some people out to manually charge it, determined the problem wasn’t with the battery, so it must be the inverter. We read error messages off the inverter screen, talked to people on the phone for hours, and finally had some guys come out to look at it. Miraculously, it was determined that the inverter had a software update pushed through remotely that didn’t fully load, so the inverter was “confused about it’s identity.” It thought it was only a grid-connected inverter, that fed solar power back to the grid, but really it’s an off-grid inverter for our house. Silly inverter. Once it recognized it’s true identity, everything started working again off-grid, except for no apparent reason sometimes the power to the house would shut off and then immediately turn itself back on. Hmm...

We spent the semester shuttling greywater samples to a Berkeley Environmental Engineering lab, driving cartons of urine to another lab perfecting urine-to-fertilizer resource recovery, and making waffles on the weekends. The cooking implements in THIMBY worked remarkably well the whole semester, and we hosted several successful dinner parties (of up to 10 people!). Grilling and porch space certainly helped with larger crowds.

Given the information about our greywater (contaminated with bacteria and organic matter, but not E. Coli thankfully), we decided to pilot an additional system, a solar concentrating technology. Typically used for solar thermal water heating, we plan to repurpose the system for solar water disinfection. The idea is to run our filtered greywater through a heat exchanger with the 90C water, and inactivate bacteria that way. The solar concentrator is set up and logging data, and will be integrated with the water loop in the fall.

Innovation never stops at the tiny house; I can imagine a day maybe a year from now where we sit back on the porch in lounge chairs (or in a hot tub hooked up to use the excess hot water from the solar concentrator), and say “Yes, everything is working perfectly as designed, and we just sit around here and use the systems and log the data through our smart Home Energy Management System (HEMS). Grad school research is the best.” We had a flurry of activity right when the semester ended and people had more time again. The HEMS infrastructure was re-established, using slightly more durable, and solder-able, perf board. An Arduino Uno connected to a Raspberry Pi provided the hardware to log the building performance data in real-time and to control heating and ventilation units remotely. We took apart the lower planter box to replace with a more traditional slow sand filter, and installed a settling tank under the planter boxes to remove turbidity and allow the UV light to function. And, we packed up the house to be “road ready” for the next THIMBY road trip adventure.

If all goes according to plan, THIMBY will drive up to Lopez Island this summer, pulled by the trusty vehicle known as “Big Red,” a 3500 series ’93 Chevy Silverado. It was an ordeal shopping around for a functional used truck that would safely tow 10,000+ lbs, but we think we’ve got the truck for the job. The idea is to test out the systems in a truly “off-grid” setting (on a piece of farm property on Lopez), with long hours of daylight and more time to make adjustments and fixes. And, to see how mobile THIMBY really is! Stay tuned for the next post on the drive and ferry crossing to the island.